Imagine a situation that you want to see only the active configuration of squid.conf which is having 3532 line, to see the configuration you have to navigate through whole file from top to bottom, use this command to make your life easier.
# grep ^[^#] squid.conf
This will show only the files which are not starting with #, means the active configuration you made in whole file, may be 5 or 10 lines.
# grep ^[^#] filename
grep – filtering command
^ – starting of the line[^#] – ^ inside [ ] having different meaning (you have to learn regular expression ), [^] means “not” # the symbol, this could be anything # or @ or $ or anything.
filename – filename